Testing of pressure parts and various structures using nondestructive testing techniques is an arduous task, particularly when testing seam welds. For example, a boiler system having multiple components in a fixed, limited amount of space may be difficult to inspect with precision. Typically, using ultrasonic techniques (UT), an operator manually scans the desired area of the structure with a hand-held UT probe that delivers signals (sound waves) through the structure and weld and receives feedback measurements as a result of the scanning. Clearly such a manual process is susceptible to inaccuracies, since a human operator's fine motor skills while traversing the structure, may not be entirely stable or consistent, which translates to less than optimal readings (e.g., missed cracks or wall degradation, false positives, and other such errors).
Since damage and failure typically begins at a weld seam of these components, it is important to inspect the welds periodically. Since the components being inspected are part of a function system, it is best to inspect them without having to remove a component, or disassemble the system.
Commonly used inspection devices have employed ultrasonic scanners that were moved manually from place to place. The resulting readings are graphed or otherwise displayed to the operator to indicate the location of flaws. A scanner that delivers a probe that can quickly non-intrusively assess the condition of a weld decreases servicing time and is valuable.
General-purpose mechanical scanners were used for inspecting the condition of welds on various shaped objects. Due to their general-purpose nature, they tended to be large and bulky.
In steam generation systems, there typically are welded pipes that carry pressurized steam. These employ welds that must be monitored periodically. Due to the tight clearances, conventional inspection devices will not fit and are not adapted to the shape.
What is needed, therefore, is a low profile inspection device that can fit into tight spaces to inspect welds of components requiring frequent inspection.